The same method serves for determining the available chlorine in other
bleaching chlorides such as sodium hypochlorite (Eau de Labarraque) and
potassium hypochlorite (Eau de Javelle), etc.
Good commercial chloride of lime usually furnishes 123-127 chlorornetric
degi-ees, corresponding with 39-40% of available chlorine ; lower qualities give
as little as 95 degrees (30% of chlorine).
BORAX AND NATURAL BORATES
The most common sodium karate is the prismatic form, NaaB407 +
ioH20 = 382-26, with 47-14% of water. There are also Octahedral borax,
Na2B407 + 5lI20 = 292-26, with 30-83% of water, and Burnt borax, Na2B407
= 202-1, free from water. The first two form crystals, prismatic or octahe-
dral, and the third a fine powder, and all dissolve in water with an alkaline
Natural borates are : Bonwitc- (magnesium borate and magnesium
chloride, 2Mg;,B801B + MgCla), Borocalcitc- or Pandcrmitc (hydratecl calcium
borate, Ca2B0Ou + 4liaO or CaB4O7 + 6H2O) and Boronatrocalcita (cal-
cium borate and sodium hydroxide).
Borax may contain the same impurities as boric acid (q.v.). In borax
and the natural borates the content of boric acid must be determined ; this
may be clone either by difference after the water and the impurities have
been determined or directly by a volumetric method.
Determination of the Boric Acid.-.....-(«) IN BORAX : about 30 grams
of the substance are dissolved, in boiled water and the solution ma.de up to
I litre. 50 c.c. of the liquid, filtered if necessary, arc titrated in presence
of a few drops of methyl orange with N/2-acid, which combines with the
Na20 and liberates all the boric acid. 50 c.c. of glycerine and 2-3 drops
of phenolphtlialein solution are then added, and the solution titrated with
N/2-alkali hydroxide (absolutely free from carbonates), as indicated under
Boric Acid (5). I c.c. of N/2-acid ~-~ 0-0155 gram NaaO and I c.c. N/2-
alkali — 0-0175 gram Ba()., ~~ 0-0955 gram NaaB4O7 -|- loll./).
(6) IN NATURAL BORATKS : 2 grains of tlu: substance are heated, in a
flask with a reflux condenser, with 50 c.c. of N-aeid. When cool, the con-
denser is rinsed out and the excess of acid neutralised with N-alkali in
presence of methyl orange. Glycerine and phenolphthalein are then added
and the free boric acid titrated with N/2-alkali as in case (a).
Crude borax may contain marked quantities of impurities (.sodium chloride
and sulphate, calcium sulphate, insoluble matters and hygroscopic water) ;
the refined product is generally pure or almost so. '.Che boronatroealeite of
S. America contains 21-44% BaOa.
Br = 79-92 (80)
A dark, brownish-red, heavy liquid emitting in the. air irritating, dense
red fumes ; soluble in about 33 parts of water, I.) — 2-99 at 15°, b.pt. 63°.
It may be contaminated with chlorine, iodine, sulphuric acid, and, organicium iodide and i gram of crystallised sodium